In the field of profile shaping wherein rotary cutters are used to shape or contour the edge of a workpiece according to a desired pattern, hand routers are generally used particularly on individual jobs not requiring large quantities of repetitive work. Routing machines normally consist of a high speed motor generally of the series wound electrical type to which is coupled a side milling tool and in addition such machines include a simple guide mechanism for adjusting the depth of tool cut in the plane formed by the cutter's axis and a line normal to the direction of cutter travel. The router cutters usually include a number of ridges defined by flutes to provide clearance for removal of cut material. Because router cutters are moved along or across the workpiece rather than through or into as a drill would be moved, the cutting ridges and clearance flutes are not of the spiral twist type found in drills or other mills. Consequently, in a router the removal of chips or cut material is mostly radial or tangential such that bending loads are imposed on the tool because the chips are unable to leave the worked surface quickly enough. When chips bog down between the cutter and the worked surface the resulting force is transmitted to the cutter tool and its support. In a hand tool such forces are generally minimal because the size of the machine limits the amount of force which can be applied, the amount of material which can be removed during one pass, and the hardness of the material to be cut.
The invention herein uses the cutting principles and techniques of a routing machine, but is adapted to remove much greater quantities of harder materials in much shorter periods of time. That is to say, the machine is designed for repetitive production which must be as fast and as accurate as possible in order to produce a finished part which will fit its companion pieces, will have a high quality finish, and will cost as little as possible. As is well known in the art, such hand routing devices can be mounted and arranged such that the workpiece may be moved into the cutter according to a camming pattern. Production machines of the above-mentioned type are designed so that the drive motors and cutting tools are much heavier in order that the loads imposed by high speed cutting will not destroy the tool or machine. The amount of work performed by production profilers is substantially greater.
Torsion is another form of loading which is imposed upon router cutting tools as a result of the nature of profile cutting. More specifically, each cutter ridge is literally scraping, conventional milling, tearing, or broaching the edge of the workpiece and tangential forces are imposed upon the cutting edges. These tangential forces result in great torsional stress about the axis of the cutter tool. The effect of such torsional loading or the torque reaction is greatest at the part of the tool farthest from the holder or cutter support, and so the cutter has a tendency to be twisted against the direction of cutter rotation. This reaction or loading is different from the loading of a drill with its spiral cutter flutes which generate axial forces as well.
As can be appreciated from the nature of the production techniques that require cutting or profiling much thicker workpieces, and/or shaping harder materials at much greater cutting rate, and/or removing substantial amounts of material and producing a very smooth and accurate reproduction of the pattern, the machine and cutting tool must be as close to rigid as possible. Any bending, chipping or breaking of the cutting tool could result in machine down time and in the production of many parts which are unsatisfactory in terms of shape, finish and quality before the problem was noted and corrected.